13th International Conference on Fracture June 16–21, 2013, Beijing, China -7- velocities of simulations are taken similar to experimental drop tests ( 2.7 m/s, 4.2 m/s, 5 m/s, 5.5 m/s, 5.8 m/s, 6.3 m/s and 6.9 m/s) and another one equal to 8 m/s. Figure 5. Shell finite elements model and simulation results. 4. Results and discussions 4.1. Perforation force Drop tests force during impact is compared to numerical results. In Fig. 6, forces are plotted for an initial velocity of 5.8 m/s. Simulation’s force is noised because of numerical instabilities. That’s the reason why a centered average numerical force is plotted. It can be noticed that the first force peak is not simulated. The numerical model does not take in consideration friction effects and failure propagation and thus the numerical force underestimates the measured force. As the measured force, the numerical force rises during the perforation until a maximal force, equal to 8.8 kN, versus 9.6 kN for the measured force. Figure 6. Force during impact versus time for an initial velocity of 5.8 m/s (test 9).
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